The CSES Problem Set contains a collection of algorithm programming practice problems. You can access the problems here: https://cses.fi/problemset/list/. This set has 400 classic problems of various categories and difficulties.

This was my practice run for ICPC. There are more than 290 accepted solutions listed here. I have also added tags for some of the problems.

• At first try to come up with a solution by yourself.
• If you can't then read some article on the associated tags and try again.
• If you still can't then you proceed to the solution. Try to understand what is going on. Then try your own approach.

Milestones:

• 29/12/2021: Solved 100th Problem
• 05/05/2022: Solved 150th Problem
• 05/12/2022: Solved 200th Problem
• 11/11/2023: Solved 250th Problem
• 14/06/2025: Solved all Searching and Sorting Problems
• 26/06/2025: Solved all Range Queries Problems
• 30/10/2025: Solved all Introductory Problems
• 07/11/2025: Solved 300th Problem

Introductory Problems

Status	Name	Tags	Link
✔	Weird Algorithm		Code
✔	Missing Number		Code
✔	Repetitions		Code
✔	Increasing Array		Code
✔	Permutations		Code
✔	Number Spiral		Code
✔	Two Knights		Code
✔	Two Sets		Code
✔	Bit Strings		Code
✔	Trailing Zeros		Code
✔	Coin Piles		Code
✔	Palindrome Reorder		Code
✔	Gray Code		Code
✔	Tower of Hanoi		Code
✔	Creating Strings		Code
✔	Apple Division		Code
✔	Chessboard and Queens		Code
✔	Raab Game I		Code
✔	Mex Grid Construction	Brute Force	Code
✔	Knight Moves Grid	BFS	Code
✔	Grid Coloring I	greedy	Code
✔	Digit Queries		Code
✔	String Reorder	greedy constructive	Code
✔	Grid Path Description		Code

Sorting and Searching

Status	Name	Tags	Link
✔	Distinct Numbers		Code
✔	Apartments		Code
✔	Ferris Wheel		Code
✔	Concert Tickets		Code
✔	Restaurant Customers		Code
✔	Movie Festival		Code
✔	Sum of Two Values		Code
✔	Maximum Subarray Sum		Code
✔	Stick Lengths		Code
✔	Missing Coin Sum		Code
✔	Collecting Numbers		Code
✔	Collecting Numbers II		Code
✔	Playlist		Code
✔	Towers		Code
✔	Traffic Lights		Code
✔	Distinct Values Subarrays	Counting	Code
✔	Distinct Values Subsequences	Counting	Code
✔	Josephus Problem I		Code
✔	Josephus Problem II	OST	Code
✔	Nested Ranges Check		Code
✔	Nested Ranges Count	Point Update Range Sum	Code
✔	Room Allocation		Code
✔	Factory Machines		Code
✔	Tasks and Deadlines		Code
✔	Reading Books		Code
✔	Sum of Three Values		Code
✔	Sum of Four Values		Code
✔	Nearest Smaller Values		Code
✔	Subarray Sums I		Code
✔	Subarray Sums II		Code
✔	Subarray Divisibility		Code
✔	Distinct Values Subarrays II		Code
✔	Array Division		Code
✔	Movie Festival II	Greedy Scheduling Binary Search	Code
✔	Maximum Subarray Sum II		Code

Dynamic Programming

Status	Name	Tags	Link
✔	Dice Combinations	Coin change DP	Code
✔	Minimizing Coins	Coin change DP	Code
✔	Coin Combinations I	Coin change DP	Code
✔	Coin Combinations II	Coin change DP	Code
✔	Removing Digits		Code
✔	Grid Paths I		Code
✔	Book Shop		Code
✔	Array Description		Code
✔	Counting Towers		Code
✔	Edit Distance		Code
✔	Longest Common Subsequence	LCS	Code
✔	Rectangle Cutting		Code
✔	Minimal Grid Path	BFS	Code
✔	Money Sums		Code
✔	Removal Game		Code
✔	Two Sets II	Knapsack DP	Code
	Mountain Range		Code
✔	Increasing Subsequence	LIS	Code
✔	Projects		Code
✔	Elevator Rides	Bitmask DP	Code
✔	Counting Tilings	Broken Profile DP Bitmask	Code
✔	Counting Numbers	Digit Dp	Code
✔	Increasing Subsequence II		Code

Graph Algorithms

Status	Name	Tags	Link
✔	Counting Rooms	BFS	Code
✔	Labyrinth	BFS	Code
✔	Building Roads	BFS DFS Forest Counting	Code
✔	Message Route	BFS	Code
✔	Building Teams	Bicoloring DFS	Code
✔	Round Trip	Cycle in undirected graph DFS	Code
✔	Monsters	BFS	Code
✔	Shortest Routes I	Single Source Shortest Path Dijkstra	Code
✔	Shortest Routes II	All Pair Shortes Path Floyd Warshall	Code
✔	High Score	Single Source Shortest Path Bellman Ford	Code
✔	Flight Discount	Single Source Shortest Path Dijkstra	Code
✔	Cycle Finding	Negative Cycle Bellman Ford	Code
✔	Flight Routes	Dijkstra	Code
✔	Round Trip II	DFS Cycle in directed graph	Code
✔	Course Schedule	Topological Sort	Code
✔	Longest Flight Route	Topological Sort DP	Code
✔	Game Routes	Topological Sort DP	Code
✔	Investigation	Dijkstra	Code
✔	Planets Queries I	Binary Lifting	Code
	Planets Queries II		Code
✔	Planets Cycles	DFS	Code
✔	Road Reparation	Minimum Spanning Tree Kruskal	Code
✔	Road Construction	DSU	Code
✔	Flight Routes Check	Strongly Connected Components	Code
✔	Planets and Kingdoms	Strongly Connected Components	Code
✔	Giant Pizza	2-SAT	Code
✔	Coin Collector	Condensation Graph Topological Sort DP	Code
✔	Mail Delivery	Euler Tour - Undirected	Code
✔	De Bruijn Sequence	De Bruijn Sequence	Code
✔	Teleporters Path	Euler Path - Directed	Code
✔	Hamiltonian Flights	Hamiltonian Path Bitmask DP	Code
✔	Knight's Tour	Hamiltonian Path Heuristics	Code
✔	Download Speed	Max Flow Min Cut Push Relabel Dinic	Code
✔	Police Chase	Max Flow Min Cut Push Relabel	Code
✔	School Dance	Max Flow``Bipartite Matching Hopkroft Carp	Code
✔	Distinct Routes	Max Flow Dinic Path reconstruction	Code

Range Queries

Status	Name	Tags	Link
✔	Static Range Sum Queries		Code
✔	Static Range Minimum Queries		Code
✔	Dynamic Range Sum Queries		Code
✔	Dynamic Range Minimum Queries		Code
✔	Range Xor Queries		Code
✔	Range Update Queries		Code
✔	Forest Queries		Code
✔	Hotel Queries		Code
✔	List Removals		Code
✔	Salary Queries		Code
✔	Prefix Sum Queries		Code
✔	Pizzeria Queries		Code
✔	Visible Buildings Queries	Binary Lifting	Code
✔	Range Interval Queries	Merge Sort Tree	Code
✔	Subarray Sum Queries		Code
✔	Subarray Sum Queries II	Segment tree	Code
✔	Distinct Values Queries		Code
✔	Distinct Values Queries II	Segment Tree	Code
✔	Increasing Array Queries	Segment tree Tree walking	Code
✔	Movie Festival Queries	Greedy Scheduling RMQ Binary Lifting	Code
✔	Forest Queries II		Code
✔	Range Updates and Sums		Code
✔	Polynomial Queries	Lazy Segment Tree	Code
✔	Range Queries and Copies	Persistent Segment Tree	Code
✔	Missing Coin Sum Queries	Iterative Segment Tree	Code

Tree Algorithms

Status	Name	Tags	Link
✔	Subordinates	Subtree DP	Code
✔	Tree Matching	Tree DP	Code
✔	Tree Diameter	Tree Diameter	Code
✔	Tree Distances I	Tree Diameter	Code
✔	Tree Distances II	Tree Rerooting DP	Code
✔	Company Queries I	Binary Lifting	Code
✔	Company Queries II	LCA	Code
✔	Distance Queries	LCA	Code
✔	Counting Paths	HLD	Code
✔	Subtree Queries	HLD	Code
✔	Path Queries	HLD	Code
✔	Path Queries II	HLD	Code
✔	Distinct Colors	MO on Tree / Sack Small to Large	Code
✔	Finding a Centroid	Centroid	Code
✔	Fixed-Length Paths I	Centroid Decomposition	Code
	Fixed-Length Paths II	Centroid Decomposition	Code

Mathematics

Status	Name	Tags	Link
✔	Josephus Queries		Code
✔	Exponentiation		Code
✔	Exponentiation II		Code
✔	Counting Divisors		Code
✔	Common Divisors		Code
✔	Sum of Divisors		Code
✔	Divisor Analysis		Code
✔	Prime Multiples		Code
✔	Counting Coprime Pairs		Code
✔	Next Prime	Segmented Sieve	Code
✔	Binomial Coefficients		Code
✔	Creating Strings II		Code
✔	Distributing Apples		Code
✔	Christmas Party		Code
	Permutation Order		Code
	Permutation Rounds		Code
✔	Bracket Sequences I		Code
✔	Bracket Sequences II		Code
✔	Counting Necklaces		Code
✔	Counting Grids		Code
✔	Fibonacci Numbers		Code
✔	Throwing Dice		Code
✔	Graph Paths I		Code
✔	Graph Paths II		Code
	System of Linear Equations		Code
	Sum of Four Squares		Code
	Triangle Number Sums		Code
✔	Dice Probability		Code
	Moving Robots		Code
	Candy Lottery	Expected Value	Code
	Inversion Probability		Code
✔	Stick Game		Code
✔	Nim Game I		Code
✔	Nim Game II		Code
✔	Stair Game		Code
✔	Grundy's Game		Code
✔	Another Game		Code

String Algorithms

Status	Name	Tags	Link
✔	Word Combinations	Trie DP	Code
✔	String Matching	Suffix array / Hashing	Code
✔	Finding Borders	Z function Prefix function / Hashing	Code
✔	Finding Periods	Z function Prefix function / Hashing	Code
✔	Minimal Rotation	Suffix Automata	Code
✔	Longest Palindrome	Manacher	Code
	All Palindromes		Code
	Required Substring		Code
✔	Palindrome Queries	Range Sum Hashing	Code
✔	Finding Patterns		Code
✔	Counting Patterns		Code
✔	Pattern Positions		Code
✔	Distinct Substrings		Code
✔	Distinct Subsequences		Code
✔	Repeating Substring	Hashing Binary Search	Code
✔	String Functions		Code
	Inverse Suffix Array		Code
✔	String Transform	Inverse Burrows Wheeler Transform	Code
✔	Substring Order I		Code
✔	Substring Order II		Code
✔	Substring Distribution	Suffix Array Longest Common Prefix	Code

Geometry

Status	Name	Tags	Link
✔	Point Location Test	Cross Product	Code
✔	Line Segment Intersection		Code
✔	Polygon Area		Code
✔	Point in Polygon		Code
✔	Polygon Lattice Points		Code
	Minimum Euclidean Distance		Code
✔	Convex Hull		Code
✔	Maximum Manhattan Distances	Chebyshev Transformation	Code
✔	All Manhattan Distances	Counting	Code
✔	Intersection Points	Range Query with Sweep Line	Code
	Line Segments Trace I		Code
	Line Segments Trace II		Code
	Lines and Queries I		Code
	Lines and Queries II		Code
✔	Area of Rectangles	Range Query and Update with Sweep Line	Code
	Robot Path		Code

Advanced Techniques

Status	Name	Tags	Link
✔	Meet in the Middle		Code
✔	Hamming Distance		Code
	Corner Subgrid Check		Code
✔	Corner Subgrid Count		Code
✔	Reachable Nodes		Code
✔	Reachability Queries		Code
✔	Cut and Paste	Implicit Treap	Code
✔	Substring Reversals	Implicit Treap	Code
✔	Reversals and Sums	Implicit Treap	Code
✔	Necessary Roads	Bridges	Code
✔	Necessary Cities	Articulation Points	Code
	Eulerian Subgraphs		Code
✔	Monster Game I	DP Convex Hull Optimization	Code
✔	Monster Game II	DP Convex Hull Optimization	Code
✔	Subarray Squares	DP Convex Hull Optimization	Code
	Houses and Schools		Code
✔	Knuth Division	DP Knuth Optimization	Code
✔	Apples and Bananas	FFT	Code
✔	One Bit Positions	FFT	Code
✔	Signal Processing	FFT	Code
✔	New Roads Queries	HLD	Code
✔	Dynamic Connectivity	Dynamic DSU	Code
✔	Parcel Delivery	Max Flow Min Cost Fixed flow	Code
✔	Task Assignment	Max Flow Min Cost	Code
✔	Distinct Routes II	Max Flow Min Cost Path reconstruction	Code

Sliding Window Problems

Status	Name	Tags	Link
✔	Sliding Window Sum		Code
✔	Sliding Window Minimum		Code
✔	Sliding Window Xor		Code
✔	Sliding Window Or	Two Stack	Code
✔	Sliding Window Distinct Values		Code
✔	Sliding Window Mode		Code
✔	Sliding Window Mex		Code
✔	Sliding Window Median		Code
✔	Sliding Window Cost		Code
✔	Sliding Window Inversions	Segment Tree	Code
	Sliding Window Advertisement		Code

Interactive Problems

Status	Name	Tags	Link
✔	Hidden Integer	Binary Search	Code
✔	Hidden Permutation	Merge Sort	Code
✔	K-th Highest Score	Binary Seach	Code
	Permuted Binary Strings		Code
	Colored Chairs		Code
	Inversion Sorting		Code

Bitwise Operations

Status	Name	Tags	Link
✔	Counting Bits		Code
✔	Maximum Xor Subarray	Trie Divide and Conquer	Code
✔	Maximum Xor Subset	Xor Basis	Code
✔	Number of Subset Xors	Xor Basis	Code
	K Subset Xors		Code
	All Subarray Xors		Code
✔	Xor Pyramid Peak		Code
	Xor Pyramid Diagonal		Code
	Xor Pyramid Row		Code
✔	SOS Bit Problem		Code
	And Subset Count		Code

Construction Problems

Status	Name	Tags	Link
✔	Inverse Inversions		Code
✔	Monotone Subsequences		Code
✔	Third Permutation	Construction	Code
✔	Permutation Prime Sums	Math Greedy	Code
✔	Chess Tournament	Greedy	Code
	Distinct Sums Grid		Code
	Filling Trominos		Code
	Grid Path Construction		Code

Advanced Graph Problems

Status	Name	Tags	Link
✔	Nearest Shops	BFS	Code
✔	Prüfer Code	Prüfer Code	Code
✔	Tree Traversals		Code
	Course Schedule II		Code
✔	Acyclic Graph Edges		Code
✔	Strongly Connected Edges	Bridge	Code
	Even Outdegree Edges		Code
✔	Graph Girth	BFS Tree	Code
	Fixed Length Walk Queries		Code
	Transfer Speeds Sum		Code
✔	MST Edge Check	DSU	Code
	MST Edge Set Check		Code
✔	MST Edge Cost	HLD DSU	Code
✔	Network Breakdown	DSU with rollback	Code
	Tree Coin Collecting I		Code
	Tree Coin Collecting II		Code
✔	Tree Isomorphism I	Tree Isomorphism rooted	Code
✔	Tree Isomorphism II	Tree Isomorphism unrooted	Code
	Flight Route Requests		Code
✔	Critical Cities	Dominator Tree	Code
✔	Visiting Cities	Dijkstra Articulation Point	Code
	Graph Coloring		Code
	Bus Companies		Code
	Split into Two Paths		Code
✔	Network Renovation	Euler Tour	Code
✔	Forbidden Cities	Block Cut Tree	Code
	Creating Offices		Code
	New Flight Routes		Code

Counting Problems

Status	Name	Tags	Link
✔	Filled Subgrid Count I	DP	Code
✔	Filled Subgrid Count II	DP Monotone stack	Code
	All Letter Subgrid Count I		Code
	All Letter Subgrid Count II		Code
	Border Subgrid Count I		Code
	Border Subgrid Count II		Code
	Raab Game II		Code
	Empty String		Code
	Permutation Inversions		Code
	Counting Bishops		Code
✔	Counting Sequences	Inclusion Exclusion Principle	Code
✔	Grid Paths II		Code
✔	Counting Permutations		Code
	Grid Completion		Code
	Counting Reorders		Code
	Tournament Graph Distribution		Code
	Collecting Numbers Distribution		Code
	Functional Graph Distribution		Code

Additional Problems I

Status	Name	Tags	Link
✔	Shortest Subsequence		Code
✔	Distinct Values Sum	Contribution Technique	Code
✔	Distinct Values Splits	DP Prefix Sum	Code
✔	Swap Game		Code
	Beautiful Permutation II		Code
✔	Multiplication Table	Binary Search Harmonic Progression	Code
✔	Bubble Sort Rounds I	Sorting	Code
	Bubble Sort Rounds II		Code
	Nearest Campsites I		Code
	Nearest Campsites II		Code
✔	Advertisement	Segment Tree	Code
✔	Special Substrings	Constructive Hashing	Code
	Counting LCM Arrays		Code
	Square Subsets		Code
	Subarray Sum Constraints		Code
	Water Containers Moves		Code
	Water Containers Queries		Code
	Stack Weights		Code
	Maximum Average Subarrays		Code
	Subsets with Fixed Average		Code
	Two Array Average		Code
	Pyramid Array		Code
	Permutation Subsequence		Code
✔	Bit Inversions		Code
✔	Writing Numbers		Code
	Letter Pair Move Game		Code
✔	Maximum Building I	Segment Tree	Code
	Sorting Methods		Code
✔	Cyclic Array	Binary Search Greedy	Code
	List of Sums		Code

Additional Problems II

Status	Name	Tags	Link
✔	Bouncing Ball Steps		Code
	Bouncing Ball Cycle		Code
	Knight Moves Queries		Code
	K Subset Sums I		Code
	K Subset Sums II		Code
	Increasing Array II		Code
	Food Division		Code
	Swap Round Sorting		Code
	Binary Subsequences		Code
✔	School Excursion	Knapsack DP Bitset	Code
	Coin Grid		Code
	Grid Coloring II		Code
	Programmers and Artists		Code
	Removing Digits II		Code
	Coin Arrangement		Code
	Replace with Difference		Code
✔	Grid Puzzle I	Max Flow Min Cut	Code
✔	Grid Puzzle II	Max Flow Max Cost	Code
✔	Bit Substrings	FFT	Code
✔	Reversal Sorting	Implicit Treap	Code
	Book Shop II		Code
	GCD Subsets		Code
	Minimum Cost Pairs		Code
	Same Sum Subsets		Code
✔	Mex Grid Queries		Code
	Maximum Building II		Code
✔	Stick Divisions	Huffman Coding greedy	Code
	Stick Difference		Code
✔	Coding Company	Open and Close Interval DP	Code
	Two Stacks Sorting		Code